This invention relates to a process and apparatus for removing moisture from a material without substantially spoiling the material. Described herein are a process of and apparatus for microwave irradiation heating, drying, dehydration, curing, disinfection, pasteurization, sterilization or vapourization of any one or any combination of one or more of these processes in the processing of materials which are typically in planar form or able to be arranged so as to be in planar form.
Planar materials in the context of this invention means any organic or inorganic material or any combination of such materials presented in its natural form or in a pre-prepared or processed form or in a transportable form suitable for processing by the process and apparatus of this invention.
Planar materials in this context may be in single or multiple sheet or composite or laminated or other form in unit size of uniform shapes and dimensions or varying sizes, shapes and dimensions or process transportation size within the limiting dimensions determined by the process and apparatus of this invention.
Planar materials in the context of this invention may also be natural or preprocessed vegetable matter in sliced, diced or granular form including herbs and spices, grain seeds and nuts, rootstock and leaf materials and chemical compounds and mineral materials in granular form or solution formxe2x80x94all capable of transportation by an enclosed or other form of conveyance having a planar configuration suitable for application within the limiting dimensions determined by the process and apparatus of this invention.
The priority application of the invention is related to the field of medical, veterinary, food and environmental diagnostics, but other industrial fields of application are equally relevant.
The world is faced with a crisis in the delivery of health care services in developing countries due to a resurgence of infectious and tropical diseases such as malaria, tuberculosis, hepatitis and filariasis.
The World Health Organization estimates that more than 2 billion persons worldwide are infected with one or other of these major diseases which are in epidemic or endemic form in many developing countries. This has created enormous diagnosis logistical and resource problems due to the masses of people involved, the land areas of the countries concerned and hopelessly inadequate infrastructure medical support facilities. These problems and health risk is compounded by the increasing mobility of the world population and relocation of displaced persons and refugees.
Malaria is endemic in many countries and is one of the most serious and complex health problems facing the world community as it enters the 21st century. It has been estimated that there are between 300 and 500 million clinical cases of malaria each year with between 2 and 3 million deaths as a result of the disease. Malaria has now reached epidemic proportions due mainly to the failure of conventional therapies against multidrug resistant strains of the malarial parasite. As the emergence of disease drug resistance escalates in all malaria endemic areas early diagnosis is critical for the application of alternative chemotherapeutic agents.
Tuberculosis kills or debilitates more adults than any other disease with more than one third of the world""s population infected with the TB bacillus. Every year 6 to 8 million people develop the disease which, if early diagnosed, can now be inexpensively and effectively treated.
Hepatitis virus has infected more than 2 billion people worldwide of which some 325 million are chronically infected carriers of the virus. Hepatitis B is directly related to approximately 2 million deaths a year. The WHO estimates that by the year 2000 there could be more than 400 million carriers of this disease.
Filariasis is a parasitic disease affecting people in tropical regions. It is highly debilitating and has serious economic and social consequences. It is estimated that 750 million people live in endemic areas with 76 countries affected and 96 million people infected.
Other diseases such as pneumonia, tetanus, trachoma, dengue fever and schistosmiasis also affect millions of people worldwide and are of increasing international concern.
Animal diseases and the contamination of land air and water resources and the environment has also led to the increasing incidence of food contamination and outbreaks of environmental diseases. These contamination diseases are expected to increase unless early diagnosis technology is introduced to permit timely remedial action to be taken.
The clinical diagnosis of malaria and many other diseases is conventionally based on clinical criteria supported by microscopic examination of whole blood. This diagnostic process is time consuming, labour intensive, expensive, requires considerable technical skills and support facilities and is not practical for mass, widespread in-field application.
Scientific technology breakthroughs have occurred in the area of reliable, accurate, simple immunochromatographic, on the spot diagnostic tests for medical, veterinary, agricultural, food and environmental applications. The scientific technology is patented worldwide and is in field use for a number of diagnostic applications.
In excess of 200 existing diagnostic fields of practice have been identified as potential markets for replacement by this immunodiagnostic testing technology.
The full scientific and human health potential benefit of this technology can only be realised on a world wide basis by the inexpensive mass production of such test kits having long shelf life, stable performance, and suitable for non refrigerated distribution for in-field use. The manufacture, packaging, shelf life, stability and reliability of the immunodiagnostic test technology is highly dependent on the controlled total or near total removal of moisture from the kit housings and conjugate materials.
The test kit housings are traditionally manufactured in cardboard material for their biodegradable qualities. Alternative inorganic materials which would be moisture free would impose serious environmental disposal problems.
The drying of diagnostic kit housings by conventional methods such as lyophilizer, hot air drying, vacuum drying, freeze drying, desiccant drying and long term low humidity storage have all proved unsuccessful for high speed high quality continuous process mass production which is necessary to guarantee the economic viability and in-field reliability of the diagnostic technology for mass application.
Objects of this invention are to provide a process and apparatus for removing moisture from a material without substantially spoiling the material.
Other objects of this invention with respect to the application of the invention in the field of immunodiagnostics are to provide a process of and apparatus for the controlled total or near total or selective or differential removal of moisture from immunodiagnostic test kit housings and other planar materials or combination of planar materials under continuous production line conditions without spoiling the material for its intended purpose or resulting in the spoiling of the immunodiagnostic test process for which the use of the material is intended due to moisture take-up of the processed housings.
A further object of this invention is to provide a process and apparatus for the controlled processing of planar materials or combination of planar materials organic or inorganic, in natural or processed form, in sheet leaf or granular or prepared or transportable planar form for controlled irradiation heating, drying dehydration pasteurisation, sterilisation, disinfection or curing or any one or more of these processes under continuous process production line conditions without spoiling the material for its intended use.
According to one embodiment of this invention there is provided a process for removing moisture from a material without substantially spoiling the material, said process comprising:
(a) subjecting the material to a controlled humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation;
(b) selectively and differentially irradiating at least one selected area of the material, the at least one selected area being less than the entire area of the material, without substantially irradiating a non-selected portion of the material, the selected and differential irradiation being in the environment with an amount of microwave irradiation effective to increase the moisture at the surface of the material whereby the partial vapour pressure of water at the surface of the material is greater than the partial vapour pressure of water of the environment whereby moisture is transferred from the surface to the environment, wherein the amount of said microwave irradiation and the selected area which is irradiated do not spoil the material; and
(c) maintaining (i) the temperature of the environment, and, (ii) the partial vapour pressure of water of said environment substantially below saturation, whereby the material is not spoiled during step (b);
said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface of the material, until a required amount of moisture has been removed from said material, without substantially reducing the surface temperature of the material and being sufficient to maintain the surface temperature of the material at substantially the same temperature as the dry bulb temperature of the environment.
A further embodiment is a material from which moisture has been removed without substantially spoiling the material by the process of the invention.
According to another embodiment of this invention there is provided an apparatus for removing moisture from a material without substantially spoiling the material, said apparatus comprising:
(a) means for subjecting the material to a controlled humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation;
(b) means for selectively and differentially irradiating at least one selected area of the material, the at least one selected area being less than the entire area of the material, without substantially irradiating a non-selected portion of the material, the selected and differential irradiation being in the environment with an amount of microwave irradiation effective to increase the moisture at the surface of the material whereby the partial vapour pressure of water at the surface of the material is greater than the partial vapour pressure of water of the environment whereby moisture is transferred from the surface of the material to the environment, wherein the amount of said microwave irradiation and the selected area which is irradiated do not spoil the material; and
(c) means for maintaining (i) the temperature of the environment, and, (ii) the partial vapour pressure of water of said environment substantially below saturation, whereby the material is not spoiled during processing when the material is irradiated with microwaves;
said amount of microwave irradiation being sufficient to substantially maintain said vapour pressure at the surface of the material, until a required amount of moisture has been removed from said material, without substantially reducing the surface temperature of the material and being sufficient to maintain the surface temperature of the material at substantially the same temperature as the dry bulb temperature of the environment.
In various forms of the process step (a) may comprise:
(a) subjecting the material to a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation; or
(a) subjecting the material to a controlled pressure and humidity environment, said environment being at a pressure, temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation or
(a) subjecting the material to a controlled pressure, temperature and humidity environment, said environment being at a pressure, temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation.
The material may be a wood pulp product. The wood pulp product may be in substantially planar form. Examples of wood pulp products are paper and cardboard. The material may be in any suitable shape of configuration which is suitable for irradiating with microwaves. For example, the material may be in the form of a card. Typically the card is made of paper or board or cardboard or other suitable material. The card may be any suitable shape (e.g. rectangular, square, triangular, circular, parallelogram, elliptical, irregular, conical, semicircular, semi elliptical, etc). Advantageously, the card may be in the form of a test strip. The card may be unfolded or folded. Advantageously, amongst its many possible uses the card may be used to support a product either on the card or adsorbed or absorbed in the card, for example.
The material may be in the form of a housing. Typically the housing is made of paper or board or cardboard or other suitable material. A housing in the form of a foldable card is especially suitable. The housing may have one, two, three, four, five or more hinge sections. A housing having one hinge section is especially suitable. The housing which may be folded as an envelope or other suitable container is also suitable. Advantageously, amongst its many possible uses the housing may be used to support a product either on the housing or adsorbed or absorbed in the housing, for example. Advantageously, the housing may be selected from the group consisting of a test kit housing, a diagnostic test kit housing and an immunodiagnostic test kit housing. Alternatively, the housing may be for other purposes such as to hold a sample of a product (e.g. perfume).
The material may be in the form of a substantially planar housing which may be selected from the group consisting of a test kit housing, a diagnostic test kit housing and an immunodiagnostic test kit housing. Typically the substantially planar housing is foldable to form the housing. Thus in use as a housing it is typically folded rather than being in a substantially planar configuration. On the other hand when a housing is subjected to the process of the invention it is typically subjected to the process when it is in a substantially planar configuration. The housing may comprise a wood pulp product such as cardboard. In particular, the immunodiagnostic test kit housing typically comprises a wood pulp product such as cardboard. Advantageously, the material is in the form of an immunodiagnostic test kit housing.
The material may be in the form of a substantially planar housing which may be selected from the group consisting of a test kit housing, a diagnostic test kit housing and an immunodiagnostic test kit housing wherein said required amount of moisture removed from said material is selected from the group consisting of absolute dryness and near measurable absolute dryness without spoiling the housing.
The material may be in the form of a substantially planar housing which may be selected from the group consisting of a test kit housing, a diagnostic test kit housing and an immunodiagnostic test kit housing a hinge section wherein said required amount of moisture removed from said material is removed by selectively and differentially irradiating said housing to control the degree of drying of the housing without spoiling the hinge section.
The material may be in the form of a substantially planar housing which may be selected from the group consisting of a test kit housing, a diagnostic test kit housing and an immunodiagnostic test kit housing having a hinge section and edges wherein said required amount of moisture removed from said material is removed by selectively and differentially irradiating said housing to control the degree of drying of the housing without spoiling the hinge section and the edges.
The material may be in the form of a substantially planar housing which may be selected from the group consisting of a test kit housing, a diagnostic test kit housing and an immunodiagnostic test kit housing having a hinge section and edges wherein said required amount of moisture removed from said material is removed by selectively and differentially irradiating said housing to control the degree of drying of the housing without spoiling the hinge section and the edges.
The material may be in the form of a substantially planar housing which may be selected from the group consisting of a test kit housing, a diagnostic test kit housing and an immunodiagnostic test kit housing having edges and wherein said required amount of moisture removed from said material is removed by selectively and differentially irradiating said housing to control the degree of drying of the housing without spoiling the edges.
The irradiating may be substantially continuous throughout the process.
Alternatively, the irradiating comprises pulses of microwave irradiation throughout the process. The irradiating may comprises pulses of microwave irradiation at a predetermined frequency of irradiation pulses to suit the processing properties of the material. The predetermined frequency of irradiation may comprise a pulse sequence duration and timing T2 of between 0.02 and 1.50 times the material transfer time T1 through a single microwave waveguide pass when operating in TE10 mode. Typically the pulse sequence duration and timing T2 is in the range of 0.25 to 2.50 seconds.
The process may be carried out under the simultaneous control of the process microwave residence time (being T1xc3x97N where N is the number of microwave waveguide passes), said material surface temperature, applied microwave power W and drying air dry bulb temperature and wet bulb temperature at a pressure selected from atmospheric pressure and sub-atmospheric pressure.
The temperature under which the process is carried out will be dependent on the material. For example, for a wood pulp product a typical temperature range is the range of 10-60xc2x0 C., typically 20-55xc2x0 C. More typically the temperature is in the range of 20-55xc2x0 C. and the partial vapour pressure of water is less than about 70% of saturation. Yet more typically the temperature is in the range of 45-55xc2x0 C. (such as at 45xc2x0 C. 46xc2x0 C., 47xc2x0 C., 48xc2x0 C., 49xc2x0 C., 50xc2x0 C., 51xc2x0 C., 52xc2x0 C., 53xc2x0 C., 54xc2x0 C. or 55xc2x0 C., for example) and the partial vapour pressure of water is less than about 30% of saturation, typically 5-30%, 4-25%, 4-20%, 4-16%, 4-15%, 4-12%, 4-10%. And even more typically the temperature is about 50xc2x0 C., 51xc2x0 C., 52xc2x0 C., 53xc2x0 C., 54xc2x0 C. or 55xc2x0 C. and the partial vapour pressure of water is about 5 to about 15% of saturation. Typically, the partial vapour pressure of water in the environment is in the range of 1-80%, more typically 3-75%, 3-70%, 3-60%, 3-50%, 3-40%, 3 30%, 3-25%, 3-20%, 3-15%, 3-12%, 3-10%, 3-8% or 3-5% of saturation.
In the apparatus of the invention (a) may comprise: means for subjecting the material in a controlled temperature and humidity environment, said environment being at a temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation;
Alternatively, in the apparatus (a) may comprise:
means for subjecting the material to a controlled pressure and humidity environment, said environment being at a pressure, temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation.
As another alternative in the apparatus of the invention (a) may comprise:
means for subjecting the material to a controlled pressure, temperature and humidity environment, said environment being at a pressure, temperature and partial vapour pressure of water which do not spoil the material, and, in which the partial vapour pressure of water of said environment is substantially below saturation.
The means for irradiating may comprise means for continuously irradiating.
Alternatively, the means for irradiating comprises means for irradiating with pulses of irradiation. Typically the means for irradiating comprises means for irradiating with pulses of irradiation at a predetermined frequency of irradiation pulses to suit the processing properties of the material.
The apparatus may comprise means to simultaneously control the process microwave residence time (being T1xc3x97N where N is the number of microwave waveguide passes), said material surface temperature, applied microwave power W and drying air dry bulb temperature and wet bulb temperature at a pressure selected from atmospheric pressure and sub-atmospheric pressure.
In the process of the invention the processing parameters are chosen (e.g. process microwave residence time, material surface temperature, applied microwave power W, humidity, environment temperature, environment pressure, drying air dry bulb temperature and web bulb temperature) so that the material does not burn, cook or incur surface damage during the irradiating with microwave irradiation so as not to spoil the material. In the process of the invention the relationships between the process microwave residence time, the applied microwave power W, process environment temperature, environment pressure, drying air dry bulb temperature vapour pressure, the product surface temperature and surface vapour pressure are important relationships and influencing factors in product processing. For any given material a certain amount of routine trial an error will normally be required in order to optimise the relationships and avoid spoiling the material.
The material may be irradiated a plurality of times, e.g. 2-8,000, more typically 2 to 5,000, even more typically 2 to 1,000, yet even more typically 2-100 and even more typically 2 to 10 (or even more typically 2 to 50, 2 to 25, 5 to 10 times) with continuous or pulsed microwave irradiation.
Typically, the amount of microwave irradiation is sufficient to substantially maintain the vapour pressure at the surface, until a required amount of moisture has been removed from said material, without substantial reduction of the surface temperature of the material.
Advantageously, the apparatus of the invention may include a surface temperature sensor such as a fibre optic temperature sensing device or an infra red sensing device to measure and monitor the surface temperature of the material.
This invention provides by way of example a process and apparatus for the high speed microwave drying of a planar material by the simultaneous integrated control of the material processing speed and surface temperature, microwave irradiation power input and processing environment dry bulb temperature and wet bulb temperature when operating under atmospheric or sub-atmospheric pressure.
The process and apparatus of the invention provide for high speed microwave processing of planar materials or materials presented for processing in planar form for controlled irradiation, heating or drying or dehydration or disinfection or pasteurization or sterilization or curing or any one or more of these processes under continuous production line conditions without spoiling the material for its intended purpose.
A process of and apparatus of the invention provide for high speed microwave drying of immunodiagnostic test kit housings to reduce the housing moisture content to absolute or near measurable absolute dryness or to a controlled specified residual moisture content when operating under continuous in-line production conditions without spoiling the housing material for its intended purpose. In the process and apparatus of the invention the required drying process depending on the material (e.g. a wood pulp product such as cardboard) can be achieved typically in less than 20 seconds processing residence time and preferably in 10 to 15 seconds and more preferably in 6 to 10 seconds or even more preferably in less than 6 seconds. In the process and apparatus of the invention in which conjugate ribbon assembled material is similarly processed under controlled temperatures below 40xc2x0 C. without adverse impact on the antibody and antigen compounds or spoiling of the material for its intended purpose.
In the process and apparatus of the invention the product being processed may be a diagnostic housing having a hinge section which may be selectively and differentially irradiated so as to control the degree of drying of the housing face material and the hinge section to avoid failure of the hinge due to excessive drying and brittlement which may otherwise occur.
In the process and apparatus of the invention controlled drying air and pre-treatment and cooling air conditions are provided by a refrigerated dehumidifying air recirculating heat pump system utilising magnetron waste heat as a recoverable heat source to supplement condenser waste heat and evaporator run-around air to water sensible heat transfer heat exchangers. The balance of energy being used to provide conditioned cooling air for end product cooling, magnetron air cooling and machine enclosure environmental control.
In the process and apparatus of the invention the material may subjected to microwave irradiation simultaneously to both faces of the material in each waveguide pass thereby creating a balancing of the forces acting on the material, thereby speeding the process, reducing the material temperature rise and eliminating warping of the material.
In the process and apparatus of the invention the controlled pre conditioned drying air, cooling air and material pre-treatment air is applied equally and simultaneously to both faces of the subject material in a manner to create a scrubbing action together with irradiation on both sides of the material thereby resulting in the processing of the material without measurable variation in material size, warping, burning, discoloration or breakdown of the cellular structure of the material or its surface treatment or otherwise spoilt for its intended purpose.
According to an embodiment of this invention in its preferred form the process will operate at the internationally approved (ISM) 2450 MHz microwave heating frequency but may also operate at other available frequencies including 896, 915, 922 and 2375 MHz. The microwave electromagnetic heating frequencies typically used in the processes of the invention 896, 915, 922 and 2450 MHzxc2x1permitted deviations which are provided by international agreement. The preferred frequency is 2450 MHz. Other microwave frequencies that may be used include those in the range 915xc2x125 to 22,125xc2x1125 megacycles/second more usually 915xc2x125 to 7,500xc2x150 megacycles/second.
The term xe2x80x9cspoilxe2x80x9d throughout the specification and claims is to be taken as meaning that a material that is spoilt is no longer suitable for its intended use because it has been spoilt. For example a material having bubbling, burn marks, brittleness, curling, limpness, warping or other undesirable characteristics would be a spoilt material.